Such rotors are used to generate energy from water, air or other fluid flows. In the operation of such a rotor, at least one rotor blade moves in the direction of or together with the fluid flow and at least one rotor blade moves against the direction of the fluid flow or against the fluid flow. For example, a wind turbine rotor is known from DE 20 2004 017 309 U1, having a rotor which is rotatable about a vertical axis, wherein the rotor blades are subdivided into a plurality of half-shell-shaped partial blades. Vertical gaps are arranged between the partial blades to allow air to pass through.